Islamist anti-Israel protesters used a police car's speakers to broadcast messages of hate during a march against Israel's defensive operation in Gaza.

The rally, which took place in the center of Frankfurt on Saturday, was mainly attended by Muslim youths and featured signs reading "Israel kills children" and "Allah is great", alongside more openly anti-Semitic banners such as "You Jews are beasts!"

A large contingent of Turkish immigrants were particularly noticeable, with one woman holding a sign saying "Game Over Israel - Tayyip is coming.." a reference to Turkey's Islamist Prime Minister Recep Tayyip Erdogan.

The initial group of 300 demonstrators swelled to a crowd of roughly 2,500, according to the Frankfurter Algemein, and police soon began to lose control, with protesters hurling rocks and bottles at police, who responded with riot-control measures.

But then, in a controversial bid to diffuse the situation, police granted use of one of their own cars to one of the rally's coordinators, who brought the crowd "under control" - by leading them in vitriolic anti-Israel chants and Islamist slogans.

The Algemein said Jewish community leaders were outraged at the move, which comes amid a rise in violent attacks on Jews and pro-Israel activists during similar rallies in France and the US.